1. Field of the Invention
This invention relates to a process, apparatus and system for forming a sterile connection (sterile docking) between two tubes.
At the present time there are a number of medical and scientific procedures which require the sterile transfer of fluids from one container to another. The only truly sterile transfer system in current use involves prejoining containers with tubes and then sterilizing the entire assembly. This is inflexible and costly since new containers cannot be added and the number of joined containers needed is often not known at the time of initial filling.
An example of the need for sterile docking is in continuous ambulatory peritoneal dialysis (CAPD). This procedure is replacing dialysis of blood outside the body in membrane diffusion cells where waste products normally removed by kidneys are washed from the blood, which is then returned to the patient. Dialysis outside of the body is a time-consuming procedure and sometimes results in damage to the blood by exposure to materials and conditions external to the body. In CAPD, the patient is required to spend time only for draining spent dialysate and replacing it with a fresh solution.
The CAPD patient has a tube connected to his or her peritoneal cavity via an implanted catheter. A tube from a bag of fresh dialysis solution is connected to the patient's tube. The fresh dialysis solution is drained from the bag into the patient's peritoneal cavity where it remains for about 3-4 hours. During this treatment period, the empty bag is folded and carried by the patient who can continue with his or her normal activities. After this treatment period, the spent dialysate is drained back into the empty bag which is then disconnected from the patient's tube. A bag of fresh dialysis solution is then connected to the patient's tube and the procedure is repeated. Connection to a new bag of dialysis solution exposes the tube ends to airborne bacteria or other contamination even though precautions are taken. No satisfactory way heretofore has existed to insure sterility in spite of the elaborate and costly precautions now employed including the use of masks, gloves, gauze strips and disinfectant solutions. Usually contamination does occur to the extent that a case of peritonitis is contracted perhaps on the average once or more a year and scar tissue from it inhibits dialysis.
Truly sterile connections could minimize the occurrence of peritonitis. Also any other treatment bags, such as for an antibiotic, bacteriostat, or other medication, could be connected as desired.
A similar need for sterile docking exists for blood bags. At present, blood from a donor is drawn into a primary bag which may be joined to one or two satellite bags, all connected and sterilized before use. These satellite bags may be needed for holding blood separated components, such as plasma or platelets; treating agents, such as bases, buffers, stabilizers for cell metabolism, other preservatives, or rejuvenants; or washes to remove a treating agent or other contaminant. Actually, it is not feasible to have preconnected bags for all the treatments which may be desired. Supplemental treatments such as fresh preservative cannot now be added sterilely during bag storage by any commercially acceptable procedure. In addition, to avoid the expense of unused satellite bags, the number of such bags is chosen based on limited, predicted needs. The inability to forecast needs well adds greatly to inventory requirements and complicates scheduling of blood donations.
Currently, very limited use is made of quality control as a time assay of the quantity and quality of components in separated blood factions. The main reason for the current limited use is that heretofore an entry into a sterile blood unit exposed the blood to bacteria, thereby requiring that the blood be used within 24 hours from entry. Hence, although the viability of stored blood components can be extended by supplemental treatments, such as adding a preservative during storage, such treatments are usually not effected.
Moreover, the primary blood bag contains anticoagulant which can be sterilized only by heat (steam); thus all preconnected bags are also sterilized by wet-sterilization techniques, i.e., steam or hot water in an autoclave apparatus. These bags are made of plasticized polyvinyl chloride (PVC), although other materials are known to be useful for constructing bags which are favorable for other reasons, such as greater oxygen permeability. Since many such materials, e.g., oxygen permeable polyethylene, are not steam sterilizable, they are not now used in preconnected systems.
A sterile docking means would permit one to effect whatever processing is desired without compromising sterility, limiting storage life or requiring the preconnection of a multitude of bags, all wet-sterilizable, without knowing which, if any, will be used.
2. References
U.S. Pat. No. 3,013,925 discloses a method of welding two joints of thermoplastic pipe wherein the inside of each end of the joints of pipe to be welded is beveled and the ends of the pipes are heated, for example by pressing the ends of the sections of pipe against a heated plate, after which the ends of the sections are forced together so that flow of softened material is to the outside of the pipe and a weld is effected substantially without formation of a bead on the inside of the welded pipe.
U.S. Pat. No. 3,035,631 discloses a tip for welding plastic parts. The tip has a knife edge at each of two opposing ends. One end of the knife is thick whereas the other is thin. The patent states that as the thin end passes through the joint, it will induce molten plastic surfaces to flow together.
U.S. Pat. No. 3,117,903 discloses a method of joining thermoplastic pipe without forming a troublesome inside ridge at the point of weld, said method involving the immersion of the ends of pipe to be welded in inert high boiling organic liquid heated above the softening temperature of the polymer forming the pipe. Thereby, the ends of the pipe are caused to expand and flare outwardly; then the pipe is withdrawn from the bath and the ends butted together.
U.S. Pat. No. 3,897,296 discloses a method of welding two plastic surfaces together by juxtapositioning the surfaces, heating the surfaces to a temperature approaching the flash point of the plastic surfaces to liquefy the surfaces, removing a portion of the liquefied surfaces to expose unoxidized surfaces therebeneath and immediately bringing the unoxidized surfaces into abutment with one another. The patent is silent as to cutting a tube as well as forming a sterile dock.
U.S. Pat. No. 3,968,195 discloses a method for making a sterile connection between two rigid tubes the free ends of which have thermoplastic diaphragms which seal them off. The free ends of each rigid tube are aligned while being spaced slightly apart, and each thermoplastic diaphragm is opened by heating. The free ends of the rigid tubes are then brought into contact and held in position under a slight pressure while the thermoplastic material cools and solidifies, thereby creating a permanent connection. This process requires tubes which have low-melting thermoplastic diaphragms on the ends which can only be used once, i.e., another connection to the same tubing cannot be made.
U.S. Pat. No. 4,209,013 discloses an improvement in a sterile connector system for continuous peritoneal dialysis in which a dialysis solution container having a transfer port is coupled to tubing extending from a patient's peritoneal cavity. The improvement comprises a flexible housing having a first area thereof for attachment to the transfer port and a second spaced area for attachment to the patient's tubing. The attachment areas define openings for enabling the transfer port and patient's tubing to extend within the interior of the flexible housing when they are attached thereto. The flexible housing has means for receiving a sterilizing fluid therein and is operable to enable the transfer port and the patient's tubing to be sterilized within the housing and also connected to each other within the housing.
U.S. Pat. No. 4,223,675 discloses a system for producing sterile, non-autoclavable body fluid containers having autoclaved liquid therein, comprising a dry-sterilized package formed of a material which is unsuitable for being subjected to autoclave conditions, said dry-sterilized package including a sterile communication with the interior of said package; an autoclavable dispenser constructed of an autoclavable substance and containing liquid which was sterilized within the dispenser, said dispenser including a sterile connector having an initially closed sterile aperture in sterile communication with the interior of the dispenser; said package sterile connector and said dispenser sterile connector being in mating engagement with each other.
"An Aseptic Fluid Transfer System for Blood and Blood Components", B. A. Myhre et al, Transfusion, Vol. 18, No. 5 pp. 546-552, Sept.-Oct. 1978, describes a process for heat sealing two aseptic fluid transfer system (AFTS) units together. The AFTS units contain a layer of Kapton.RTM. film (an aromatic polyimide resin which is stable at relatively high temperatures). A pair of dies, one of which is flat and one of which has a raised "H" shaped area, are brought together under a pressure of 100 psi (6.9.times.10.sup.6 dynes per square centimeter) with the AFTS units disposed between the dies. The temperature of the dies is raised to 200.degree. C. (392.degree. F.) over a period of 45 seconds. The dies are withdrawn and upon removal of the AFTS units from the dies, the AFTS units are heat sealed together by a seal surrounding an opening between the AFTS units. Blood bags constructed with an AFTS unit attached can thereby be joined. This system is slow and requires specially constructed units that can only be used once.
Other patents directed to sterile connection apparatuses or methods include U.S. Pat. Nos. 4,157,723, 4,242,310 and 4,253,500.